2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * This program is the ssh daemon. It listens for connections from clients,
6 * and performs authentication, executes use commands or shell, and forwards
7 * information to/from the application to the user client over an encrypted
8 * connection. This can also handle forwarding of X11, TCP/IP, and
9 * authentication agent connections.
11 * As far as I am concerned, the code I have written for this software
12 * can be used freely for any purpose. Any derived versions of this
13 * software must be clearly marked as such, and if the derived work is
14 * incompatible with the protocol description in the RFC file, it must be
15 * called by a name other than "ssh" or "Secure Shell".
17 * SSH2 implementation:
19 * Copyright (c) 2000 Markus Friedl. All rights reserved.
21 * Redistribution and use in source and binary forms, with or without
22 * modification, are permitted provided that the following conditions
24 * 1. Redistributions of source code must retain the above copyright
25 * notice, this list of conditions and the following disclaimer.
26 * 2. Redistributions in binary form must reproduce the above copyright
27 * notice, this list of conditions and the following disclaimer in the
28 * documentation and/or other materials provided with the distribution.
30 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
31 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
33 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
34 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
35 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
39 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 RCSID("$OpenBSD: sshd.c,v 1.187 2001/04/03 23:32:12 markus Exp $");
45 #include <openssl/dh.h>
46 #include <openssl/bn.h>
47 #include <openssl/hmac.h>
66 #include "myproposal.h"
68 #include "pathnames.h"
78 int allow_severity = LOG_INFO;
79 int deny_severity = LOG_WARNING;
86 #ifdef HAVE___PROGNAME
87 extern char *__progname;
92 /* Server configuration options. */
93 ServerOptions options;
95 /* Name of the server configuration file. */
96 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
99 * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
100 * Default value is AF_UNSPEC means both IPv4 and IPv6.
103 int IPv4or6 = AF_INET;
105 int IPv4or6 = AF_UNSPEC;
109 * Debug mode flag. This can be set on the command line. If debug
110 * mode is enabled, extra debugging output will be sent to the system
111 * log, the daemon will not go to background, and will exit after processing
112 * the first connection.
116 /* Flag indicating that the daemon is being started from inetd. */
119 /* Flag indicating that sshd should not detach and become a daemon. */
120 int no_daemon_flag = 0;
122 /* debug goes to stderr unless inetd_flag is set */
125 /* Saved arguments to main(). */
130 * The sockets that the server is listening; this is used in the SIGHUP
133 #define MAX_LISTEN_SOCKS 16
134 int listen_socks[MAX_LISTEN_SOCKS];
135 int num_listen_socks = 0;
138 * the client's version string, passed by sshd2 in compat mode. if != NULL,
139 * sshd will skip the version-number exchange
141 char *client_version_string = NULL;
142 char *server_version_string = NULL;
145 * Any really sensitive data in the application is contained in this
146 * structure. The idea is that this structure could be locked into memory so
147 * that the pages do not get written into swap. However, there are some
148 * problems. The private key contains BIGNUMs, and we do not (in principle)
149 * have access to the internals of them, and locking just the structure is
150 * not very useful. Currently, memory locking is not implemented.
153 Key *server_key; /* ephemeral server key */
154 Key *ssh1_host_key; /* ssh1 host key */
155 Key **host_keys; /* all private host keys */
158 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
162 * Flag indicating whether the RSA server key needs to be regenerated.
163 * Is set in the SIGALRM handler and cleared when the key is regenerated.
165 int key_do_regen = 0;
167 /* This is set to true when SIGHUP is received. */
168 int received_sighup = 0;
170 /* session identifier, used by RSA-auth */
171 u_char session_id[16];
174 u_char *session_id2 = NULL;
175 int session_id2_len = 0;
177 /* record remote hostname or ip */
178 u_int utmp_len = MAXHOSTNAMELEN;
180 /* Prototypes for various functions defined later in this file. */
181 void do_ssh1_kex(void);
182 void do_ssh2_kex(void);
184 void ssh_dh1_server(Kex *, Buffer *_kexinit, Buffer *);
185 void ssh_dhgex_server(Kex *, Buffer *_kexinit, Buffer *);
188 * Close all listening sockets
191 close_listen_socks(void)
194 for (i = 0; i < num_listen_socks; i++)
195 close(listen_socks[i]);
196 num_listen_socks = -1;
200 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
201 * the effect is to reread the configuration file (and to regenerate
205 sighup_handler(int sig)
208 signal(SIGHUP, sighup_handler);
212 * Called from the main program after receiving SIGHUP.
213 * Restarts the server.
218 log("Received SIGHUP; restarting.");
219 close_listen_socks();
220 execv(saved_argv[0], saved_argv);
221 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
226 * Generic signal handler for terminating signals in the master daemon.
227 * These close the listen socket; not closing it seems to cause "Address
228 * already in use" problems on some machines, which is inconvenient.
231 sigterm_handler(int sig)
233 log("Received signal %d; terminating.", sig);
234 close_listen_socks();
235 unlink(options.pid_file);
240 * SIGCHLD handler. This is called whenever a child dies. This will then
241 * reap any zombies left by exited c.
244 main_sigchld_handler(int sig)
246 int save_errno = errno;
249 while (waitpid(-1, &status, WNOHANG) > 0)
252 signal(SIGCHLD, main_sigchld_handler);
257 * Signal handler for the alarm after the login grace period has expired.
260 grace_alarm_handler(int sig)
262 /* Close the connection. */
265 /* Log error and exit. */
266 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
270 * Signal handler for the key regeneration alarm. Note that this
271 * alarm only occurs in the daemon waiting for connections, and it does not
272 * do anything with the private key or random state before forking.
273 * Thus there should be no concurrency control/asynchronous execution
277 generate_ephemeral_server_key(void)
282 verbose("Generating %s%d bit RSA key.",
283 sensitive_data.server_key ? "new " : "", options.server_key_bits);
284 if (sensitive_data.server_key != NULL)
285 key_free(sensitive_data.server_key);
286 sensitive_data.server_key = key_generate(KEY_RSA1,
287 options.server_key_bits);
288 verbose("RSA key generation complete.");
290 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
293 sensitive_data.ssh1_cookie[i] = rand & 0xff;
300 key_regeneration_alarm(int sig)
302 int save_errno = errno;
303 signal(SIGALRM, SIG_DFL);
309 sshd_exchange_identification(int sock_in, int sock_out)
312 int remote_major, remote_minor;
315 char buf[256]; /* Must not be larger than remote_version. */
316 char remote_version[256]; /* Must be at least as big as buf. */
318 if ((options.protocol & SSH_PROTO_1) &&
319 (options.protocol & SSH_PROTO_2)) {
320 major = PROTOCOL_MAJOR_1;
322 } else if (options.protocol & SSH_PROTO_2) {
323 major = PROTOCOL_MAJOR_2;
324 minor = PROTOCOL_MINOR_2;
326 major = PROTOCOL_MAJOR_1;
327 minor = PROTOCOL_MINOR_1;
329 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
330 server_version_string = xstrdup(buf);
332 if (client_version_string == NULL) {
333 /* Send our protocol version identification. */
334 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
335 != strlen(server_version_string)) {
336 log("Could not write ident string to %s.", get_remote_ipaddr());
340 /* Read other side's version identification. */
341 memset(buf, 0, sizeof(buf));
342 for (i = 0; i < sizeof(buf) - 1; i++) {
343 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
344 log("Did not receive identification string from %s.",
345 get_remote_ipaddr());
348 if (buf[i] == '\r') {
350 /* Kludge for F-Secure Macintosh < 1.0.2 */
352 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
356 if (buf[i] == '\n') {
361 buf[sizeof(buf) - 1] = 0;
362 client_version_string = xstrdup(buf);
366 * Check that the versions match. In future this might accept
367 * several versions and set appropriate flags to handle them.
369 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
370 &remote_major, &remote_minor, remote_version) != 3) {
371 s = "Protocol mismatch.\n";
372 (void) atomicio(write, sock_out, s, strlen(s));
375 log("Bad protocol version identification '%.100s' from %s",
376 client_version_string, get_remote_ipaddr());
379 debug("Client protocol version %d.%d; client software version %.100s",
380 remote_major, remote_minor, remote_version);
382 compat_datafellows(remote_version);
384 if (datafellows & SSH_BUG_SCANNER) {
385 log("scanned from %s with %s. Don't panic.",
386 get_remote_ipaddr(), client_version_string);
391 switch(remote_major) {
393 if (remote_minor == 99) {
394 if (options.protocol & SSH_PROTO_2)
400 if (!(options.protocol & SSH_PROTO_1)) {
404 if (remote_minor < 3) {
405 packet_disconnect("Your ssh version is too old and "
406 "is no longer supported. Please install a newer version.");
407 } else if (remote_minor == 3) {
408 /* note that this disables agent-forwarding */
413 if (options.protocol & SSH_PROTO_2) {
422 chop(server_version_string);
423 debug("Local version string %.200s", server_version_string);
426 s = "Protocol major versions differ.\n";
427 (void) atomicio(write, sock_out, s, strlen(s));
430 log("Protocol major versions differ for %s: %.200s vs. %.200s",
432 server_version_string, client_version_string);
436 packet_set_ssh2_format();
440 /* Destroy the host and server keys. They will no longer be needed. */
442 destroy_sensitive_data(void)
446 if (sensitive_data.server_key) {
447 key_free(sensitive_data.server_key);
448 sensitive_data.server_key = NULL;
450 for(i = 0; i < options.num_host_key_files; i++) {
451 if (sensitive_data.host_keys[i]) {
452 key_free(sensitive_data.host_keys[i]);
453 sensitive_data.host_keys[i] = NULL;
456 sensitive_data.ssh1_host_key = NULL;
457 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
461 list_hostkey_types(void)
463 static char buf[1024];
466 for(i = 0; i < options.num_host_key_files; i++) {
467 Key *key = sensitive_data.host_keys[i];
473 strlcat(buf, key_ssh_name(key), sizeof buf);
474 strlcat(buf, ",", sizeof buf);
479 if (i > 0 && buf[i-1] == ',')
481 debug("list_hostkey_types: %s", buf);
486 get_hostkey_by_type(int type)
489 for(i = 0; i < options.num_host_key_files; i++) {
490 Key *key = sensitive_data.host_keys[i];
491 if (key != NULL && key->type == type)
498 * returns 1 if connection should be dropped, 0 otherwise.
499 * dropping starts at connection #max_startups_begin with a probability
500 * of (max_startups_rate/100). the probability increases linearly until
501 * all connections are dropped for startups > max_startups
504 drop_connection(int startups)
508 if (startups < options.max_startups_begin)
510 if (startups >= options.max_startups)
512 if (options.max_startups_rate == 100)
515 p = 100 - options.max_startups_rate;
516 p *= startups - options.max_startups_begin;
517 p /= (double) (options.max_startups - options.max_startups_begin);
518 p += options.max_startups_rate;
520 r = arc4random() / (double) UINT_MAX;
522 debug("drop_connection: p %g, r %g", p, r);
523 return (r < p) ? 1 : 0;
526 int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
527 int startup_pipe; /* in child */
530 * Main program for the daemon.
533 main(int ac, char **av)
537 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
541 struct sockaddr_storage from;
542 const char *remote_ip;
545 struct linger linger;
547 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
548 int listen_sock, maxfd;
552 int ret, key_used = 0;
554 __progname = get_progname(av[0]);
561 /* Initialize configuration options to their default values. */
562 initialize_server_options(&options);
564 /* Parse command-line arguments. */
565 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:dDiqQ46")) != -1) {
574 config_file_name = optarg;
577 if (0 == debug_flag) {
579 options.log_level = SYSLOG_LEVEL_DEBUG1;
580 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
583 fprintf(stderr, "Too high debugging level.\n");
597 options.log_level = SYSLOG_LEVEL_QUIET;
600 options.server_key_bits = atoi(optarg);
603 options.ports_from_cmdline = 1;
604 if (options.num_ports >= MAX_PORTS) {
605 fprintf(stderr, "too many ports.\n");
608 options.ports[options.num_ports++] = atoi(optarg);
611 options.login_grace_time = atoi(optarg);
614 options.key_regeneration_time = atoi(optarg);
617 if (options.num_host_key_files >= MAX_HOSTKEYS) {
618 fprintf(stderr, "too many host keys.\n");
621 options.host_key_files[options.num_host_key_files++] = optarg;
624 client_version_string = optarg;
625 /* only makes sense with inetd_flag, i.e. no listen() */
629 utmp_len = atoi(optarg);
633 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
634 fprintf(stderr, "Usage: %s [options]\n", __progname);
635 fprintf(stderr, "Options:\n");
636 fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
637 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
638 fprintf(stderr, " -i Started from inetd\n");
639 fprintf(stderr, " -D Do not fork into daemon mode\n");
640 fprintf(stderr, " -q Quiet (no logging)\n");
641 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
642 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
643 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
644 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
645 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
646 _PATH_HOST_KEY_FILE);
647 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
648 fprintf(stderr, " -4 Use IPv4 only\n");
649 fprintf(stderr, " -6 Use IPv6 only\n");
653 SSLeay_add_all_algorithms();
656 * Force logging to stderr until we have loaded the private host
657 * key (unless started from inetd)
660 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
661 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
666 /* Read server configuration options from the configuration file. */
667 read_server_config(&options, config_file_name);
669 /* Fill in default values for those options not explicitly set. */
670 fill_default_server_options(&options);
672 /* Check that there are no remaining arguments. */
674 fprintf(stderr, "Extra argument %s.\n", av[optind]);
678 debug("sshd version %.100s", SSH_VERSION);
680 /* load private host keys */
681 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
682 for(i = 0; i < options.num_host_key_files; i++)
683 sensitive_data.host_keys[i] = NULL;
684 sensitive_data.server_key = NULL;
685 sensitive_data.ssh1_host_key = NULL;
686 sensitive_data.have_ssh1_key = 0;
687 sensitive_data.have_ssh2_key = 0;
689 for(i = 0; i < options.num_host_key_files; i++) {
690 key = key_load_private(options.host_key_files[i], "", NULL);
691 sensitive_data.host_keys[i] = key;
693 error("Could not load host key: %.200s: %.100s",
694 options.host_key_files[i], strerror(errno));
695 sensitive_data.host_keys[i] = NULL;
700 sensitive_data.ssh1_host_key = key;
701 sensitive_data.have_ssh1_key = 1;
705 sensitive_data.have_ssh2_key = 1;
708 debug("private host key: #%d type %d %s", i, key->type,
711 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
712 log("Disabling protocol version 1. Could not load host key");
713 options.protocol &= ~SSH_PROTO_1;
715 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
716 log("Disabling protocol version 2. Could not load host key");
717 options.protocol &= ~SSH_PROTO_2;
719 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
720 log("sshd: no hostkeys available -- exiting.");
724 /* Check certain values for sanity. */
725 if (options.protocol & SSH_PROTO_1) {
726 if (options.server_key_bits < 512 ||
727 options.server_key_bits > 32768) {
728 fprintf(stderr, "Bad server key size.\n");
732 * Check that server and host key lengths differ sufficiently. This
733 * is necessary to make double encryption work with rsaref. Oh, I
734 * hate software patents. I dont know if this can go? Niels
736 if (options.server_key_bits >
737 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
738 options.server_key_bits <
739 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
740 options.server_key_bits =
741 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
742 debug("Forcing server key to %d bits to make it differ from host key.",
743 options.server_key_bits);
747 #ifdef HAVE_SCO_PROTECTED_PW
748 (void) set_auth_parameters(ac, av);
751 /* Initialize the log (it is reinitialized below in case we forked). */
752 if (debug_flag && !inetd_flag)
754 log_init(__progname, options.log_level, options.log_facility, log_stderr);
757 * If not in debugging mode, and not started from inetd, disconnect
758 * from the controlling terminal, and fork. The original process
761 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
764 #endif /* TIOCNOTTY */
765 if (daemon(0, 0) < 0)
766 fatal("daemon() failed: %.200s", strerror(errno));
768 /* Disconnect from the controlling tty. */
770 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
772 (void) ioctl(fd, TIOCNOTTY, NULL);
775 #endif /* TIOCNOTTY */
777 /* Reinitialize the log (because of the fork above). */
778 log_init(__progname, options.log_level, options.log_facility, log_stderr);
780 /* Initialize the random number generator. */
783 /* Chdir to the root directory so that the current disk can be
784 unmounted if desired. */
788 signal(SIGPIPE, SIG_IGN);
790 /* Start listening for a socket, unless started from inetd. */
793 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
799 * We intentionally do not close the descriptors 0, 1, and 2
800 * as our code for setting the descriptors won\'t work if
801 * ttyfd happens to be one of those.
803 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
804 if (options.protocol & SSH_PROTO_1)
805 generate_ephemeral_server_key();
807 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
808 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
810 if (num_listen_socks >= MAX_LISTEN_SOCKS)
811 fatal("Too many listen sockets. "
812 "Enlarge MAX_LISTEN_SOCKS");
813 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
814 ntop, sizeof(ntop), strport, sizeof(strport),
815 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
816 error("getnameinfo failed");
819 /* Create socket for listening. */
820 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
821 if (listen_sock < 0) {
822 /* kernel may not support ipv6 */
823 verbose("socket: %.100s", strerror(errno));
826 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
827 error("listen_sock O_NONBLOCK: %s", strerror(errno));
832 * Set socket options. We try to make the port
833 * reusable and have it close as fast as possible
834 * without waiting in unnecessary wait states on
837 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
838 (void *) &on, sizeof(on));
841 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
842 (void *) &linger, sizeof(linger));
844 debug("Bind to port %s on %s.", strport, ntop);
846 /* Bind the socket to the desired port. */
847 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
849 error("Bind to port %s on %s failed: %.200s.",
850 strport, ntop, strerror(errno));
854 listen_socks[num_listen_socks] = listen_sock;
857 /* Start listening on the port. */
858 log("Server listening on %s port %s.", ntop, strport);
859 if (listen(listen_sock, 5) < 0)
860 fatal("listen: %.100s", strerror(errno));
863 freeaddrinfo(options.listen_addrs);
865 if (!num_listen_socks)
866 fatal("Cannot bind any address.");
870 * Record our pid in /var/run/sshd.pid to make it
871 * easier to kill the correct sshd. We don't want to
872 * do this before the bind above because the bind will
873 * fail if there already is a daemon, and this will
874 * overwrite any old pid in the file.
876 f = fopen(options.pid_file, "wb");
878 fprintf(f, "%u\n", (u_int) getpid());
882 if (options.protocol & SSH_PROTO_1)
883 generate_ephemeral_server_key();
885 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
886 signal(SIGHUP, sighup_handler);
888 signal(SIGTERM, sigterm_handler);
889 signal(SIGQUIT, sigterm_handler);
891 /* Arrange SIGCHLD to be caught. */
892 signal(SIGCHLD, main_sigchld_handler);
894 /* setup fd set for listen */
897 for (i = 0; i < num_listen_socks; i++)
898 if (listen_socks[i] > maxfd)
899 maxfd = listen_socks[i];
900 /* pipes connected to unauthenticated childs */
901 startup_pipes = xmalloc(options.max_startups * sizeof(int));
902 for (i = 0; i < options.max_startups; i++)
903 startup_pipes[i] = -1;
906 * Stay listening for connections until the system crashes or
907 * the daemon is killed with a signal.
914 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
915 fdset = (fd_set *)xmalloc(fdsetsz);
916 memset(fdset, 0, fdsetsz);
918 for (i = 0; i < num_listen_socks; i++)
919 FD_SET(listen_socks[i], fdset);
920 for (i = 0; i < options.max_startups; i++)
921 if (startup_pipes[i] != -1)
922 FD_SET(startup_pipes[i], fdset);
924 /* Wait in select until there is a connection. */
925 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
926 if (ret < 0 && errno != EINTR)
927 error("select: %.100s", strerror(errno));
928 if (key_used && key_do_regen) {
929 generate_ephemeral_server_key();
936 for (i = 0; i < options.max_startups; i++)
937 if (startup_pipes[i] != -1 &&
938 FD_ISSET(startup_pipes[i], fdset)) {
940 * the read end of the pipe is ready
941 * if the child has closed the pipe
942 * after successful authentication
943 * or if the child has died
945 close(startup_pipes[i]);
946 startup_pipes[i] = -1;
949 for (i = 0; i < num_listen_socks; i++) {
950 if (!FD_ISSET(listen_socks[i], fdset))
952 fromlen = sizeof(from);
953 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
956 if (errno != EINTR && errno != EWOULDBLOCK)
957 error("accept: %.100s", strerror(errno));
960 if (fcntl(newsock, F_SETFL, 0) < 0) {
961 error("newsock del O_NONBLOCK: %s", strerror(errno));
964 if (drop_connection(startups) == 1) {
965 debug("drop connection #%d", startups);
969 if (pipe(startup_p) == -1) {
974 for (j = 0; j < options.max_startups; j++)
975 if (startup_pipes[j] == -1) {
976 startup_pipes[j] = startup_p[0];
977 if (maxfd < startup_p[0])
978 maxfd = startup_p[0];
984 * Got connection. Fork a child to handle it, unless
985 * we are in debugging mode.
989 * In debugging mode. Close the listening
990 * socket, and start processing the
991 * connection without forking.
993 debug("Server will not fork when running in debugging mode.");
994 close_listen_socks();
1002 * Normal production daemon. Fork, and have
1003 * the child process the connection. The
1004 * parent continues listening.
1006 if ((pid = fork()) == 0) {
1008 * Child. Close the listening and max_startup
1009 * sockets. Start using the accepted socket.
1010 * Reinitialize logging (since our pid has
1011 * changed). We break out of the loop to handle
1014 startup_pipe = startup_p[1];
1015 for (j = 0; j < options.max_startups; j++)
1016 if (startup_pipes[j] != -1)
1017 close(startup_pipes[j]);
1018 close_listen_socks();
1021 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1026 /* Parent. Stay in the loop. */
1028 error("fork: %.100s", strerror(errno));
1030 debug("Forked child %d.", pid);
1032 close(startup_p[1]);
1034 /* Mark that the key has been used (it was "given" to the child). */
1035 if ((options.protocol & SSH_PROTO_1) &&
1037 /* Schedule server key regeneration alarm. */
1038 signal(SIGALRM, key_regeneration_alarm);
1039 alarm(options.key_regeneration_time);
1045 /* Close the new socket (the child is now taking care of it). */
1048 /* child process check (or debug mode) */
1049 if (num_listen_socks < 0)
1054 /* This is the child processing a new connection. */
1057 * Disable the key regeneration alarm. We will not regenerate the
1058 * key since we are no longer in a position to give it to anyone. We
1059 * will not restart on SIGHUP since it no longer makes sense.
1062 signal(SIGALRM, SIG_DFL);
1063 signal(SIGHUP, SIG_DFL);
1064 signal(SIGTERM, SIG_DFL);
1065 signal(SIGQUIT, SIG_DFL);
1066 signal(SIGCHLD, SIG_DFL);
1067 signal(SIGINT, SIG_DFL);
1070 * Set socket options for the connection. We want the socket to
1071 * close as fast as possible without waiting for anything. If the
1072 * connection is not a socket, these will do nothing.
1074 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1076 linger.l_linger = 5;
1077 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1079 /* Set keepalives if requested. */
1080 if (options.keepalives &&
1081 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
1083 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1086 * Register our connection. This turns encryption off because we do
1089 packet_set_connection(sock_in, sock_out);
1091 remote_port = get_remote_port();
1092 remote_ip = get_remote_ipaddr();
1094 /* Check whether logins are denied from this host. */
1096 /* XXX LIBWRAP noes not know about IPv6 */
1098 struct request_info req;
1100 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, NULL);
1103 if (!hosts_access(&req)) {
1108 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1110 #endif /* LIBWRAP */
1111 /* Log the connection. */
1112 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1115 * We don\'t want to listen forever unless the other side
1116 * successfully authenticates itself. So we set up an alarm which is
1117 * cleared after successful authentication. A limit of zero
1118 * indicates no limit. Note that we don\'t set the alarm in debugging
1119 * mode; it is just annoying to have the server exit just when you
1120 * are about to discover the bug.
1122 signal(SIGALRM, grace_alarm_handler);
1124 alarm(options.login_grace_time);
1126 sshd_exchange_identification(sock_in, sock_out);
1128 * Check that the connection comes from a privileged port.
1129 * Rhosts-Authentication only makes sense from priviledged
1130 * programs. Of course, if the intruder has root access on his local
1131 * machine, he can connect from any port. So do not use these
1132 * authentication methods from machines that you do not trust.
1134 if (remote_port >= IPPORT_RESERVED ||
1135 remote_port < IPPORT_RESERVED / 2) {
1136 debug("Rhosts Authentication disabled, "
1137 "originating port not trusted.");
1138 options.rhosts_authentication = 0;
1141 if (!packet_connection_is_ipv4() &&
1142 options.kerberos_authentication) {
1143 debug("Kerberos Authentication disabled, only available for IPv4.");
1144 options.kerberos_authentication = 0;
1148 /* If machine has AFS, set process authentication group. */
1155 packet_set_nonblocking();
1157 /* perform the key exchange */
1158 /* authenticate user and start session */
1161 do_authentication2();
1164 do_authentication();
1168 /* Cleanup user's ticket cache file. */
1169 if (options.kerberos_ticket_cleanup)
1173 /* The connection has been terminated. */
1174 verbose("Closing connection to %.100s", remote_ip);
1178 #endif /* USE_PAM */
1193 BIGNUM *session_key_int;
1194 u_char session_key[SSH_SESSION_KEY_LENGTH];
1196 u_int cipher_type, auth_mask, protocol_flags;
1200 * Generate check bytes that the client must send back in the user
1201 * packet in order for it to be accepted; this is used to defy ip
1202 * spoofing attacks. Note that this only works against somebody
1203 * doing IP spoofing from a remote machine; any machine on the local
1204 * network can still see outgoing packets and catch the random
1205 * cookie. This only affects rhosts authentication, and this is one
1206 * of the reasons why it is inherently insecure.
1208 for (i = 0; i < 8; i++) {
1210 rand = arc4random();
1211 cookie[i] = rand & 0xff;
1216 * Send our public key. We include in the packet 64 bits of random
1217 * data that must be matched in the reply in order to prevent IP
1220 packet_start(SSH_SMSG_PUBLIC_KEY);
1221 for (i = 0; i < 8; i++)
1222 packet_put_char(cookie[i]);
1224 /* Store our public server RSA key. */
1225 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1226 packet_put_bignum(sensitive_data.server_key->rsa->e);
1227 packet_put_bignum(sensitive_data.server_key->rsa->n);
1229 /* Store our public host RSA key. */
1230 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1231 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1232 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1234 /* Put protocol flags. */
1235 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1237 /* Declare which ciphers we support. */
1238 packet_put_int(cipher_mask_ssh1(0));
1240 /* Declare supported authentication types. */
1242 if (options.rhosts_authentication)
1243 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1244 if (options.rhosts_rsa_authentication)
1245 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1246 if (options.rsa_authentication)
1247 auth_mask |= 1 << SSH_AUTH_RSA;
1249 if (options.kerberos_authentication)
1250 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1253 if (options.kerberos_tgt_passing)
1254 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1255 if (options.afs_token_passing)
1256 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1258 if (options.challenge_reponse_authentication == 1)
1259 auth_mask |= 1 << SSH_AUTH_TIS;
1260 if (options.password_authentication)
1261 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1262 packet_put_int(auth_mask);
1264 /* Send the packet and wait for it to be sent. */
1266 packet_write_wait();
1268 debug("Sent %d bit server key and %d bit host key.",
1269 BN_num_bits(sensitive_data.server_key->rsa->n),
1270 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1272 /* Read clients reply (cipher type and session key). */
1273 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1275 /* Get cipher type and check whether we accept this. */
1276 cipher_type = packet_get_char();
1278 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1279 packet_disconnect("Warning: client selects unsupported cipher.");
1281 /* Get check bytes from the packet. These must match those we
1282 sent earlier with the public key packet. */
1283 for (i = 0; i < 8; i++)
1284 if (cookie[i] != packet_get_char())
1285 packet_disconnect("IP Spoofing check bytes do not match.");
1287 debug("Encryption type: %.200s", cipher_name(cipher_type));
1289 /* Get the encrypted integer. */
1290 session_key_int = BN_new();
1291 packet_get_bignum(session_key_int, &slen);
1293 protocol_flags = packet_get_int();
1294 packet_set_protocol_flags(protocol_flags);
1296 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1299 * Decrypt it using our private server key and private host key (key
1300 * with larger modulus first).
1302 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1303 /* Server key has bigger modulus. */
1304 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1305 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1306 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1307 get_remote_ipaddr(),
1308 BN_num_bits(sensitive_data.server_key->rsa->n),
1309 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1310 SSH_KEY_BITS_RESERVED);
1312 if (rsa_private_decrypt(session_key_int, session_key_int,
1313 sensitive_data.server_key->rsa) <= 0)
1315 if (rsa_private_decrypt(session_key_int, session_key_int,
1316 sensitive_data.ssh1_host_key->rsa) <= 0)
1319 /* Host key has bigger modulus (or they are equal). */
1320 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1321 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1322 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1323 get_remote_ipaddr(),
1324 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1325 BN_num_bits(sensitive_data.server_key->rsa->n),
1326 SSH_KEY_BITS_RESERVED);
1328 if (rsa_private_decrypt(session_key_int, session_key_int,
1329 sensitive_data.ssh1_host_key->rsa) < 0)
1331 if (rsa_private_decrypt(session_key_int, session_key_int,
1332 sensitive_data.server_key->rsa) < 0)
1336 * Extract session key from the decrypted integer. The key is in the
1337 * least significant 256 bits of the integer; the first byte of the
1338 * key is in the highest bits.
1341 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1342 len = BN_num_bytes(session_key_int);
1343 if (len < 0 || len > sizeof(session_key)) {
1344 error("do_connection: bad session key len from %s: "
1345 "session_key_int %d > sizeof(session_key) %lu",
1346 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1349 memset(session_key, 0, sizeof(session_key));
1350 BN_bn2bin(session_key_int,
1351 session_key + sizeof(session_key) - len);
1353 compute_session_id(session_id, cookie,
1354 sensitive_data.ssh1_host_key->rsa->n,
1355 sensitive_data.server_key->rsa->n);
1357 * Xor the first 16 bytes of the session key with the
1360 for (i = 0; i < 16; i++)
1361 session_key[i] ^= session_id[i];
1365 int bytes = BN_num_bytes(session_key_int);
1366 char *buf = xmalloc(bytes);
1369 log("do_connection: generating a fake encryption key");
1370 BN_bn2bin(session_key_int, buf);
1372 MD5_Update(&md, buf, bytes);
1373 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1374 MD5_Final(session_key, &md);
1376 MD5_Update(&md, session_key, 16);
1377 MD5_Update(&md, buf, bytes);
1378 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1379 MD5_Final(session_key + 16, &md);
1380 memset(buf, 0, bytes);
1382 for (i = 0; i < 16; i++)
1383 session_id[i] = session_key[i] ^ session_key[i + 16];
1385 /* Destroy the private and public keys. They will no longer be needed. */
1386 destroy_sensitive_data();
1388 /* Destroy the decrypted integer. It is no longer needed. */
1389 BN_clear_free(session_key_int);
1391 /* Set the session key. From this on all communications will be encrypted. */
1392 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1394 /* Destroy our copy of the session key. It is no longer needed. */
1395 memset(session_key, 0, sizeof(session_key));
1397 debug("Received session key; encryption turned on.");
1399 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1400 packet_start(SSH_SMSG_SUCCESS);
1402 packet_write_wait();
1406 * SSH2 key exchange: diffie-hellman-group1-sha1
1413 if (options.ciphers != NULL) {
1414 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1415 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1417 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1418 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1419 myproposal[PROPOSAL_ENC_ALGS_STOC] =
1420 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1422 if (options.macs != NULL) {
1423 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1424 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1426 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1428 kex = kex_start(myproposal);
1430 kex->client_version_string=client_version_string;
1431 kex->server_version_string=server_version_string;
1432 kex->load_host_key=&get_hostkey_by_type;
1434 /* start key exchange */
1435 dispatch_run(DISPATCH_BLOCK, &kex->newkeys, kex);
1437 session_id2 = kex->session_id;
1438 session_id2_len = kex->session_id_len;
1441 /* send 1st encrypted/maced/compressed message */
1442 packet_start(SSH2_MSG_IGNORE);
1443 packet_put_cstring("markus");
1445 packet_write_wait();